docs: def __make_tree(self):
          """Build a tree using lxml.html.builder and our subtrees"""
  
          # create div with "container" class
          div = E.DIV(E.CLASS("container"))
  
          # append header with title
          div.append(E.H2(self.__title))
  
          # next, iterate through subtrees appending each tree to div
          for subtree in self.__subtrees:
              div.append(subtree.get_html())
  
          # Connect div to body
          body = E.BODY(div)
  
          # attach body to html
          self.__htmltree = E.HTML(
              E.HEAD(
                  E.TITLE(self.__title)
                  ),
              body
              )